of springfield



F. C. HOLTZ Aug. 4, 1931. Re. 18,145

MOTOR Original Filed May 25. 1925 /6` 5 y f4 ,2 ffy-f ff ffm@ ff /cP Z4 g Z4" 52 Z' /a /g ,g /5 3 Z7 Z2 j: MyW- Ronued Aug. 4, 1.931'

PATENT OF FICE FREDERICK C. HOLTZ, OI SPRINGFIELD, ILLINOIS, ASSIGNOB T0 BANGAHO ELECTRIC `(120., OF SPRINGFIELD, ILLINOIS,

A conronnou' or rumors MOTOR 'original no. runs-1o, ama :february 1s, 19so,`,sria1 no. asassv, ma my 85,1929. appucatm for reissue led November 15,.

This invention. relates to alternating current electric motors, and more particularly to motors of the reaction type.

One of the main objects of my invention is to provide a relatively small synchronous motor of the reaction type particularly adapted for driving the mechanism oi" clocks,` demand registers, or similar devices. A further objet is to' provide a motor of this lo type of comparatively simple and inexpensive construction, which is rugged and compact, has low synchronous speeds, 'and in which the torque per watt in-put is high- Another object is to provide a motor of this 15 'character in which the stresses in the rotor are balanced, thus. eliminating noise due to vibration and producing a motor which is noiseless, or practically so, in its operation, a

necessa characteristic of motors to be used o for win ing clocks and like purposes.

Further objects and advantages of mydnvention will appear from the detail description.

In the drawings: V

Figure 1 is a side view of a motor constructed in accordance with my invention;

Figure 2 is a vertical sectional view through the motor in the plane of the axis thereof, parts being shown in elevation, on an enlarged scale;

Figure 3 is a section taken substantially 0n line 3*-3 of Figure 2, the rotor being partly broken away;

Figure 4 is a detail edge view, partly 1n section, of .a modified form of rotor;

Figure 5 is an outer face view, partly broken away, of a modified form of stator.

A motor constructed in accordance with my invention comprises a cylindrical stator, a coil within the stator, the stator being provided with an annular air gap in the magnetic circuit thereof, and a. rotor having magneticelements projecting into the air gap. In the articular construction illustrated, by way -o example, I provide a tubular core 1 of magnetic material, such as soft iron or highly magneticsteel. This core is reduced at one end to provide a neck 2 and a shoulder 3 at the inner end thereof. A cup shaped 60 casing 4, which is also of magnetic material,

1930. -Serial lo. 498,028.

such as soft iron or highly magnetic steel, has its'head 5 fitted upon the neck 2 and seating upon shoulder 3. Flange or body 6 of this casing is concentric with core 1 and extends toward the other end thereof.

The vcore Vis reduced at its other` end to provide a neck 7 upon which is mounted a disc 8 which is formed of highly magnetic material,'such as soft iron or a sultable steel. This disc Vis secured u on neck 7 by turning over the .outer end ci) the neck to provide a beadv9.' This bead cooperates with shoulder 10 of the core for tightly. securing the disc in position u on the core.v

A plate 11, pre erably of a non-magnetic material, such as brass, 'is dis osed about neck 2 of the core at the outer ac e of head 5 of casing 4. The outer end ofl neck 2 is 'turned over to provide a bead 12 which coacts with shoulder 3 for tightly securing the plate 11 and head 5 on the core. If desired, neck 2 may be exteriorly threadedhead 5 and plate 11 being screwed onto thisneck` the outer end of which;l is then rolled over to provide the bead 12. It is not essential, however, that the plate and the head of the casing'be screwed onto neck 2 which ma be Athreaded or not, as desired, and depen ing upon conditions. I also contemplate threading neck 7 and screwing disc 8 onto this l neck, if this seems desirable at an time.

A plate 13, similar to plate 11', 1s disposed adjacent the outer face of disc 8, but spaced an appreciable distance therefrom. The plates 11 and 13 are secured together -by means of screws 14 'which pass through ears 15 of the plate and screw into the ends of spacing members or pillars 16 having reduced terminal elements 17 which fit into Prior to securingidisc 8 ,upon neck 7 of core 1, coil 22 is placed about the core and within casing 6. This coil lits tightly about core 1 and` is tightly clamped betwen head 5 and head 8. The disc, being of less diameter thanv the interior diameter of casing 4, defines with the adjacent edge portion of 5 body 6 of the casing, an annular air gap 23 which is concentric with casing 4. I thus provide a cylindrical stator within which the coil isdisposed, this stator having an annular air gap defined by the-adlacent edge portions of casing 4 and disc 8, such portions constituting the terminal elements of the 24 of casing 4. .There may be considerable variation lin the number as well as size and spacing` kof the teeth either on the.v casing or on the disc, and it is not essential that both the disc and the casing be serrated or toothed, as one only of these members need be toothed. I have found, however, that very satisfactory results are obtained by providing both the casing and the disc 8 with an equal number of teeth which correspond in width and spacing.

Core 1 is of tubular construction, the bore thereof being of stepped formation and decreasing in diameter from neck 12. A bearing ring 26 is mounted in the intermedlate portion of the bore of c'ore 1 and is secured against axial movement therein by a s'crew plug 27 screwed into the largest portlon of the bore of core 1, through neck 2. Sleeve 21 has the outer\end portion of its bore of stepped formation and receives a bearing ring 28 secured in position' between an in terior shoulder in the sleeve and a screw plug 29 which screws into theouter end of the sleeve. A rotor shaft 30 is rotatably mountedin the bearing collars 26 and 28 bymeans of reduced end trunnions 31. A pinion 32 is secured on shaft 30 and is adapted suitable non-magnetic material. A plurality i0 of pins 36 are secured in the disc 34 and project inwardly therefrom into the air gap 23. These pins preferably correspond in number and spacing to the teeth of disc 8 and casing 4, though this is not essential as the number i5 of pins can be varied within wide limits.

The speed of the rotor, in R. P. M.is`deter mine by the formula f 120F Sz where F is the frequency of the alternating current supply and P corresponds to the number of cooperating pairs of stator polar projections or teeth. y

As stated, it is not essential that the rotor have the same number of pins as there are polar projections, as by making the number of pins in the rotor any sub-multiple of the cooperating pairs of stator polar projections, the formula still holds good. In fact, it is possible to remove any number of the pins of the rotor, down to the last pin, without altering the formula. By making the number of pins in the rotor less than and prime tothe number of cooperating pairs of stator projections the speed of therotor may be reduced. In this case the formula becomes where R is the number of pins in the rotor prime to P. While such construction is conducive to quite low speed, a motor in which the number of pins in the rotor is appreciably less than the number of stator polar projections is generally less quiet in operation than when the pins in the rotor are equal in number to the cooperating pairs o stator polar projections. This is probably due to some slight inaccuracy in balance of the rotor. By employing a greater number of pins, the vibrations due to any inaccurac 1n balance of the rotor is'greatly reducedy or eliminated with the result that the motor is practically noiseless in operation. A further advantage of employing the same number of pins in the rotor as there are pairs of polar projections in the stator is that this construction results in higher torque than is possible with any other combination of pins and polar projections.

By my constructon above set forth, I render it possible to provide a large number of poles within a comparativel small space, which gives high torque an low synchrof nous speed, which are desirable characteristics of motors of this type.

In the particular motor illustrated, I employ 48 poles, that is, 48 teeth or projections on Icasing 4 and on disc 8, and use 48 pins on the stator which, with a cycle alternating current gives a speed of 150 R. P. M. in accordance with the above stated formula.

The pins 36 of the rotor are disclosed as spaced an appreciable ldistance from the teeth of the casing and the teeth of the disc 8. In ractice the diameter of the pins should be suc as to practically span the air ga between the aligned projections or teeth o casing 4 and discs 8, only such clearance being provided as is essential for mechanical considerations. In the operation of the motor, when coil 22 is connected into an alternating current circuit, by means of the leads 22 provided for this urpose, a magnetic circuit is set up throng the stator, this .circuit in i Vhen the pins 36 are disposed in alignment with the spaces 24l and 25'L between the teeth 24 and 25 of casing 4 and discs 8, respectivel the reluctance of the magnetic circuit of the stator is a'maximum As the pins approach alignment with the pairs of teeth or polar rejections of the disc 8 and casing 4, the reliictance of the air gap decreases, and when the coil 22 is energized serves to pull the rotor in the direction in which the pins 36 are e'ected by the magnetic ux.

The motor operates in accordance with the known theory of reaction motors, and when the rotor is brought up to its pro er operating speed in accordance with the a ve stated formula, it will lock into step with the rotating fields created, and will.therea fter runv synchronously with considerable torque.

In Figure 4, I have illustrated a modified form of rotor. This form comprises a disc 37 of a suitable non-magnetic material into which is set a collar 38 of a magnetic material, the inner edge of this collar being ser- `rated to `rovide teeth 39 corresponding to pins 36 o the rotor of Figures 2 and 3. The disc 37 may conveniently be formed of a condensation product molded into shape, `such disc being molded about the collar 38. The disc may be secured on the rotor shaft in any suitable manner, as by being molded thereon, or secured thereto by any other known means. A rotor constructed in this manner operates in the same manner as the rotor of Figures 2 and 3, the rotor being so disposed that the teeth 39 thereof extend into the air gap 23.

The motor illustrated in Figures 1, 2, and 3 is not self-starting. This motor can be rendered self-starting, however, by providing a disc 40 of a non-magnetic material (Figure and which is a. good conductor of electricity, disposed between an inner disc 41 and an outer disc 42 secured on neck 7 of the core, these discs replacing the disc 8 of Figure 2. Discs 41 and 42 are formed of magnetic material, and are toothed in the same manner-as disc 8, the teeth of the outer disc 42 being disposed slightly inadvance of the teeth of the inner disc 41 in relation to the direction of rotation of the rotor, it

being considered in this figure that the rotor turns in a clockwise direction.

When the circuit through coil 22 is closed, Foucault or eddy currents are setup in the magnetic field in the annular air ga) copper disc 40 and create a strong shifting 23, it

being understoodv that the discs 41 an 42 aro idiscposed inthe same relation to the'adjacent of body 6 of casing' 4, as disc 8 in Fi ure 2. This shifting-magnetic field is closel'y analogous to a rotating magnetic field' and acts upon the elements of the rotor Vwhich cause rotation thereof under suicient torque to bring the rotor up to proper speed where it' will lock magnetically into step and run synchronously. By reversing the relation between the teeth of the discs 41 and 42, that is, b disposing the teeth of disc 42 in advance of t e teeth of disc 41, in the opposite direction to that illustrated in Figure 5, the direc- -project into the air gap Ain such manner as to tion of rotation of the rotor will be reversedA in accordance with well established principles. In self-starting motors the teeth of projections of the casing 4 may be made of less depth or, in some instances, may be entirely dispensed with.

What I claim is 1. In an electric motor of the character described, a stator comprising a core and a cup-shaped casing secured to the core Uand having close magnetic coupling therewith, the core and the casing being of magnetic rinaterial, a coil disposed about the core and within the casing with one end adjacent the casing head, a disc of magnetic material disposed adjacent the other end of the casing iand spaced therefrom, said disc having close magnetic coupling with the core, the disc having spaced projections extending toward the casing and spaced therefrom, said projections and the adjacent end of the casing defining an annular air gap, and a rotor comprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into said air gap.

2. n an electric motor of the character described, a substantially cylindrical stator of magnetic material comprising a core and end heads Vclosely coupled magnetically to the core, said stator having an air gap therein concentric with the core and being provided Y with spaced elements disposed adjacent and substantially in the plane of the air gap, a. coil disposed within the stator, and a rotor comprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into said air gap.

3. In an electric motor of the'character described, a stator comprising a core, a vcupshaped casing secured thereon at one end, said core and casing being of magnetic material, a disc of magnetic material secured on the core at the other end of the casing and spaced therefrom, the disc and the adjacent en'd of the casing defining an annular air gap, the stator having spacedy elements disposed substantially in the plane of said gap, a coil disposed labout the core and withln the casing, Aand a rotorcomprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into the air ap. y g 4. In an electric motor of the character described, a substantially cylindrical stator of magnetic material comprising a body and end heads magnetically coupled thereto, said stator having a concentric air gap and being provided with spaced elements disposed adjacent and substantially in the plane of the air gap, a ,coil disposed within the stator and aving magnetic coupling therewith, and a rotor comprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into said air gap.

5. In an electric motor of the character described, a magnetic core, a cup-shaped casing of ma etic material secured on the core, a disc o magnetic material secured on the core and ldisposed Within the open end of the casing in concentric spaced relation thereto, a coil mounted about the core and within the casing, the adjacent terminal elements of the metallic path of flow of the magnetic iiux through the stator structure defining an an- I nular air gap, one of said elements being yprovided with spaced projections disposed substantially in the plane of said gap, and a,

lrotor comprising a non-magnetic support and a lplurality of ma etic elements carried thereby'and projecting into said air gap.

, plate, a cup-shaped casing of ma 6. In an electric motor of the character described, a magnetic core, a cup-shaped casing secured on said core, said casing being of magnetic material, a disc of ma netic material secured on the core within t e open end of the casing and in concentric spaced relation thereto, a coil mounted about the core and lwithin the casing, the periphery of the disc being toothed and the adjacent edge ortion of the casing being similarly too ed, and a rotor comprising a non-magneticsupport and a lurality of magnetic lelements carried there y and projecting between the disc and the adjacent edge portion of the casing.

7. In an electric motor of the character described, a 'frame comprising front and back plates secured together in spaced relation, a core of magnetic material secured to the back etic material secured about the core and tween the same and the back plate, a disc of magnetic material secured on the core within the open end of the casing and in concentric relation thereto, said discbeing of lessl diameter than the interior diameter of the casing and defining with the adjacent edge portion thereof an annular air p, the periphery of the disc being toothe a supporting sleeve carried by the front plate, a rotorl shaft 'rotatably mounted insaid sleeve and in the core,a coil disposed about `said'core and-within the casing, and arotor secured on said shaft and described, a substantially cylindrical stator of magnetic material comprising a. cupshaped casing and a disc disposed within one end of the casing in concentricb s aced relation thereto and defining therewit an annular air gap, a coil disposed within the casing between the other end thereof and the disc,

vthe periphery of the disc being serrated to provide a plurality of radially projecting teeth and the adjacent edge of the-casin also being serrated to provide a plurality o teeth, the teeth of the disc and the teet the casing being similar in width and spacing and disposed in alignment, and a rotor comprising a plurality of magnetic elements projecting into said air gap, the elements `of the rotor correspondin in number and spacing to the teeth of the isc.

10. In an electric motor of the character described, a rotor com rising a disc of nonmagnetic material, an 4a collar set into the Ydisc and provided with a plurality of axially projecting magnetic elements.

11. In an electric motor of the character described, a rotor comprising a. dise of nonmagnetic material, and a collar of magnetic material set into the disc at one side thereof, said collar being serrated to provide a plurality of spaced axially projecting magnetic elements.

12. In an electric motor of the character of non-magnetic material of high electrical conductivity secured between said two discs,

the-two magnetic discs having their peripheral portions serrated to. provide radially projectingteeth. Y Y

14. In .an electric motor of the character described, a stator element comprising two 3 outer discs of magnetic material and an vinner disc vof non-magnetic material and hi h electrical conductivity. secured between t e outer discs, the 'outer discs havingtheir peripheral portions serrated to providel spacer-I` radially projecting teeth and the teeth of said outer discs belng disposed out of alignment.

15. In an electric motor of the character described, a. stator comprising, a core, a. cupshaped casing member secured to the core and having close magnetic coupling there- 4and within the casing member with one end adjacent the head thereof, one of said members being provided with projections extending toward and spaced from the othermember, and a rotor provided with elements disposed outwardly of and Aadjacent said other member to be acted upon by the magnetic flux incident to energizing of the coil by an alternating current for rotating said rotor.

16. In an electric motor of the character described, a stator comprising, a cup-shaped casing member of magnetic material, a core of magnetic material having close magnetic coupling with the head of the casing member and a disc member of magnetic material disposed adjacent the other end of the casing member and having close magnetic coupling with the core, one of said members .being provided with spaced projections extending toward and spaced from the other member, and arotor adjacent the disc member and provided with elements extending inwardly of the stator substantially axially thereof and' disposed outwardly of and adjacent said other member to be acted upon by the magnetic fiux.

incident to ener izingl of the coil by an alternating current or rotating said rotor.

17. In an electric motor of the character described, a stator comprising a cup-shaped casing member of magnetic material, a core of magnetic material secured at one end to the head of the casing member and a disc member of magnetic material secured' upon the other end of the core member adjacent the other end of the casing member, one of said members being provided with spaced projections extending toward and spaced from the other of said members, and a rotor adjacent the disc member and provided with elements extending inwardly of the stator substantially axially thereof and disposed outwardly of and adjacent said projections to be acted upon by the magnetic flux incident to energizing of the coil by an alternating current for rotating said rotor.

18. In an electric motor of the character described, a stator comprising, a cup-shaped casing member of magnetic material, a core of magnetic material having close magnetic coupling with the 'head of the casing member posed adjacent the other end of the casing member and having close magnetic coupling with the core, one of said members being provided with spaced projections extending toward and spaced from the other member, and a rotor adjacent the disc member and provided with magnetic elements extendin in- .vardly of the stator substantially axlally thereof and disposed outwardly of and adj acent said projections.

19. In an electric motor of the character described, a stator comprising a cup-shaped casing member of magnetic material, a core of magnetic material secured at one end to the head of the casing member and a disc member of -magnetic material secured upon the other end of the core member adjacent the other end of the casing member, one of said members being provided with spaced projections extending toward and spaced from the other of said members, and a rotor adjacent the disc member and provided with magnetic elements extending lnwardly of the stator substantially axially thereof and disposed outwardly of and adjacent said projections.

20. In an electric motor of the character described, a stator comprising, a cupshaped casing member of ma netic material, a core of magnetic material aving close magnetic coupling with the head of the casing member and a dlsc member of magnetic material disposed adjacent the other end of the casing member and having close magnetic coupling with the core, one of said members being provided with spaced projections extending toward and spaced from the other member, and a rotor provided with magnetic elements extending inwardly of the stator substantially axially thereof and disposed outwardly of and adjacent one of said members to be acted upon by the magnetic fiux incident to energizing ofthe coil by an alternating current for rotating said rotor.

21. In a synchronous motor, a stator comprising two annular elements of magnetic material concentrically disposed and comprisin portions in closely spaced relation and a apted to have an alternating flux field created therebetween, projections on one of said fplortions forming polar members in said flux eld, means forming a magnetic circuit between said stator elements and includin a coil adapted to create said alternating ux field when energized by an alternating current, and a rotor coactin with said flux field.

In witness whereof, hereunto subscribe my name this 5th day of November, A. D.,

FREDERICK C. HOLTZ.

and a disc member of magnetic material dis- 

